Material for making ablative structures

ABSTRACT

The present material constituting so-called &#39;&#39;&#39;&#39;ablative&#39;&#39;&#39;&#39; structures for the protection of missile members exposed to very high temperatures is realized by winding on the walls of the missile member to be protected, a flat braid formed of warp and weft yarns of thermoresistant material disposed obliquely in relation to the selvedges of the braid. A rectilinear reinforcing yarn is disposed along each of the opposite selvedges of the braid.

United States Patent Inventor Jacques Louis Dulles Paris, France Appl. No. 681,188

Filed Nov. 7, 1967 Patented June 8, 1971 Assignee Technique du Verre Tlsse Paris, France Priority Nov. 8, 1966 France MATERIAL FOR MAKING ABLATIVE STRUCTURES 2 Claims, 5 Drawing Figs.

Int. D04c 1/02, D04c 1/06 run of Search References Cited UNITED STATES PATENTS 1/1968 Meserole 87/7X 2/1921 Morris 87/7X 4/1947 Fraim 87/7UX 4/1949 Gregg 87/7X FOREIGN PATENTS 6/1893 Switzerland 87/7 5/1901 Switzerland 87/7 Primary Examiner-John Petrakes Attorney- Linton & Linton ABSTRACT: The present material constituting so-called ablative" structures for the protection of missile members exposed to very high temperatures is realized by winding on the walls of the missile member to be protected, a flat braid formed of warp and weft yarns of thermoresistant material disposed obliquely in relation to the selvedges of the braid. A

rectilinear reinforcing yarn is disposed along each of the opposite selvedges of the braid.

PATENTED JUN 8 I97! 583 275 IN VE'NT'OR JACQUES LOUIS DUFLOS By QWM HTTORNEYS 1 MATERIAL FOR MAKING ABLATIVE STRUCTURES It is known to use reinforced stratified materials for making parts such as sheath or covers for protecting the cones or points of missiles, spacecrafts or the inner walls of jet nozzles. These parts are destined to undergo the so-called ablation" phenomenon caused by the very high temperatures to which they are exposed due to the action of the fluid acting thereon, and at the same time they must constitute an efficient insulation for the parts to be protected thereby.

It is also known that the so-called ablation" phenomenon consists on the one hand of a partial decomposition of the material constituting the protection elements, this decomposition being attended by the building up of a coked layer, and on the other hand of a surface erosion of the material. As a rule, it is endeavored on the one hand to promote the partial decomposition of the material in order to cause the coked layer to build up rapidly and thus protect the inner mass of the material, and on the other hand to avoid the erosion of this material.

To obtain this twofold result it is necessary that the strata constituting said stratified plastic material of the protection member have a pronounced inclination in relation to the wall of the part to be protected, and therefore in relation to the direction of flow either of the air stream in the case of a missile nose or cone or the gaseous stream in the case of a jet nozzle. In fact, if the strata constituting the material were disposed parallel to the direction of flow of the surrounding medium causing the heating, this would promote the erosion or peeling" of the material and therefore its deterioration.

According to the specific applications contemplated, the strata are inclined at variable angles such as 30, 45, 60, 90, or intermediate values. Thus, the erosion caused by the thermal influence of the surrounding medium is limited to the surface ends of the strata due to the anchorage of the layers in the internal mass of the stratified structure which remains unchanged. Moreover, with this arrangement, that portion of the material which is to be decomposed by volatilization in order to absorb one fraction of the heat energy and thus create a zone of lower temperature at the outer periphery of the protection material will volatilize more readily under the influence of the heat flux.

Up to now the materials used in the manufacture of these stratified elements consisted of strips cut askew in generally preimpregnated fabrics consisting of refractory metals, refractory fibers such as silica fibers, carbon fibers or other fibers capable of absorbing a major portion of the heat energy'by volatilization such as polyamides, polyimides, polyesters, low melting point metals, etc. These strips cut askew were subsequently assembled end to end to constitute a tape of adequate length which in many cases had to be further cut into narrower strips. Then, this tape was wound on the member or part to be protected so that its surface formed a wide angle with respect to the wall of said member or part (30, 45, 60, 90 etc.).

This known method is attended by many obvious drawbacks, such as considerable handlings, the use of a large number of machines for cutting the strips and binding them end to end, etc. Moreover, since these tapes have to be wound on members having as a rule a substantially circular cross-sec tional contour, such as the noses of missiles, the edges of the tape will tend to become distorted and more particularly the yarns constituting these tapes will spread fanwise along the outer edges and tend to rave] out.

It is the essential object of the present invention to avoid these inconveniences by providing a tape of the type broadly set forth hereinabove, of which the manufacture is both simple and rapid and can be carried out at a relatively low cost, this tape further possessing greatly improved mechanical properties.

To this end the present invention provides a tape obtained by braiding yarns in the conventional manner, these yarns being of the type set forth hereinabove, with a view to provide a braided tape wherein the yarns are disposed obliquely in relation to the edges of the tape. It is clear that the angle of inclination of the braided yarns may be variable, for example of the order of 45. Advantageously, in each tape selvedge, i.e. inside the two opposite sides, a rectilinear yarn will preserve the nonalignment of the selvedges while permitting the distortion of the tape body.

Other features and advantages of this invention will appear as the following description proceeds with reference to the accompanying drawing in which:

FIG. 1 is a fragmentary diagrammatic sectional view showing a missile nose or cone covered by a protection sheath;

FIG. 2 is a perspective view of a piece of tape braided according to this invention;

FIG. 3 is a fragmentary plane view from above of a coiled tape, and

FIGS. 4 and 5 illustrate in vertical section, with parts broken away, jet nozzles made from the material of this invention.

In FIG. 1 there is shown diagrammatically by way of example a conical missile nose 1 to be protected against the excessive heat developed by its frictional contact with the surrounding atmosphere during the missile operation. Of course, the shape and nature of the member to be protected may differ from those suggested herein. As already explained, the protection of this member is obtained by winding a tape 2 in such a manner that the plane of the tape be constantly strongly inclined in relation to the wall of the member to be protected, or at right angles thereto. The adjacent turns of the tape are abutting to each other.

In FIG. 4 there is shown diagrammatically a jet nozzle 6 comprising on its inner wall the tape of this invention which is wound to constitute strata 7 disposed with their main surfaces extending substantially at right angles to the inner wall of the jet nozzle 6. This jet nozzle may be bound externally by a preimpregnated glass yarn in order to increase its bursting strength. However, from the thermal point of view this conventional arrangement is not so advantageous as that illustrated in FIG. 5 wherein the strata 9 are inclined in relation to the inner surface of the jet nozzle 6 in the same direction as the heat flow shown by the arrow 8. This preferred arrangement, wherein the strata 9 have somewhat the same function as the tiles of a roof, permits of reducing the heat conductivity of the material while preventing an abnormally high deterioration of the internal layers thereof.

The tape according to this invention is made from an initial braiding operation by using yarns suitable for the specific application contemplated, these yarns being prepared for example from silica or carbon fibers, refractory or metal yarns, natural, artificial or synthetic textile yarns having a low melting point, according to the specific function to be devolved to the protection coating. The braiding operation is carried out by using a suitable known machine capable of producing a braided tape (as shown in FIG. 2) wherein the weft and warp yarns 3 and 4 are disposed obliquely, for example with a 45 inclination, in relation to the edges of the tape. It will be readily understood that this tape may be made with any desired length and have any desired width.

During the manufacture of the braided tape, reinforcing yams 5 of adequate nature may advantageously be included, these yarns being preferably of same nature as the yarns 3, 4, along and inside the two edges of the tape. These reinforcing yarns 5 are rectilinear and adapted to prevent the distortion of the tape selvedges in the longitudinal direction, the tape structure being allowed on the other hand to undergo a certain elastic distortion widthwise, between the selvedges, as a consequence of the slipping of the oblique or skew yarns 3, 4 in relation to each other. This tape structure is also advantageous in that it facilitates the winding of the tape on the member I, for it will readily accommodate the curvature of the wall without developing creases. In fact, the possibility for the yarns 3, 4 to move slightly in relation to each other will cause the yarns to be tighter along the edge 10 having the smaller radius of curvature, these yarns being slightly spaced fanwise from each other along the outer edge 7.

braid, said braid being rolled around said member having a pronounced inclination in relation to the wall of said member, the opposite selvedges of the braid having each a rectilinear reinforcing yarn, one of these rectilinear yarns being closely applied against the wall of said member.

2. Covering forming a so-called ablative structure as claimed in claim 1, wherein said rectilinear reinforcing yarns are constituted with the same thermoresistant material as the oblique yarns ofsaid braid. 

2. Covering forming a so-called ''''ablative'''' structure as claimed in claim 1, wherein said rectilinear reinforcing yarns are constituted with the same thermoresistant material as the oblique yarns of said braid. 